1. Field of the Invention
The present invention relates to a method of driving a touch panel.
2. Discussion of the Related Art
In order to measure the magnitude of capacitance of each sensing node of a touch panel, a method of applying a pulse sequence of a specific frequency through driving lines by a driving unit and measuring signals received through sensing lines by a sensing unit is generally used. Here, as the frequency of the pulse sequence, a frequency having the lowest level of noise may be selected to suppress influence of various environmental noise sources (charger noise, fluorescent lamp noise, etc.). Further, the sensing unit may use a proper signal processing technique to extract only a signal component of the corresponding frequency.
In general, in touch detection, it may be judged that touch is generated if a response input to the sensing unit when all sensing nodes are not touched is used as a reference value, and a current input response is changed by more than a designated amount or range as compared to the reference value. For such judgment, absolute response measurement at the respective sensing nodes is required. During a process of directly measuring absolute responses, a dynamic range of signals received by the sensing unit needs to be considered.
In order to increase sensing signal quality, the intensity of signals received by the sensing unit needs to be increased as compared to noise, or a sensing time needs to be extended. The intensity of signals received by the sensing unit may be increased as compared to noise by raising a voltage level of the pulse sequence applied to the driving lines. Further, in order to elongate the sensing time at sensing nodes, a multiplexing technique of simultaneously driving a plurality of driving lines, a frequency division multiplexing technique, or a code division multiplexing technique may be used.
However, an increase in the voltage level of the pulse sequence or use of the multiplexing technique may increase the dynamic range of the signals received by the sensing unit and increase the size and complexity of an analog front-end of the sensing unit. Further, in case of multiplexing, the intensity of the signals of unit sensing nodes during data conversion is reduced, and thus multiplexing may be susceptible to quantization noise or circuit noise.